From DE 600 01 023 T2 a shifting device of a geared variable-speed transmission is known, in which sliding sleeves can be displaced axially by actuating means in the form of gearshift forks associated therewith, in order by virtue of the axial movement concerned to select an associated transmission ratio of the geared variable-speed transmission in a controlled manner. In this context it is generally known that the sliding sleeves are in each case arranged in a rotationally fixed and axially movable manner on a transmission shaft which, in addition, supports a loose wheel at least on one side close to the sliding sleeve concerned. In this case these loose wheels are fitted to rotate freely on the transmission shaft and mesh permanently with pinions of a further transmission shaft arranged as a countershaft or as a parallel input or output shaft. The gear ratios of the geared variable-speed transmission that can be engaged are then defined in accordance with the tooth number ratios of the gearwheels that mesh with one another in each case. When any particular sliding sleeve moves from a neutral position toward an engaging position in the direction of the loose wheel concerned, when the engaging position is reached the loose wheel is coupled by the sliding sleeve to the transmission shaft and thereby the rotational speeds and torques defined in each case are transmitted from the one transmission shaft to the other transmission shaft.
In DE 600 01 023 T2 the shift forks of the individual sliding sleeves are designed to be axially displaceable on a common control shaft, which by virtue of a pinion arranged at its end can be rotated selectively by an electric control element. In addition a cylinder is positioned on the control shaft and firmly connected thereto, which cylinder has on an outer diameter a groove that is curved in the axial direction. Furthermore, on the cylinder is fitted a sleeve which engages with a pin formed on its inside diameter in the groove of the cylinder, so that when the control shaft is rotated the sleeve moves axially along the cylinder in accordance with the shape of the cylinder groove. On its outside diameter the sleeve has shift fingers which, depending on the angular position of the sleeve, come in contact with one of the shift forks and accordingly transmit the axial movement of the sleeve to the fork concerned. During this, in order to adjust the particular angular position of the sleeve, the sleeve is connected by gearing to an intermediate shaft which, in turn, is in contact with the control shaft by way of a gearwheel.
When the control shaft is rotated by the electric control element the sleeve is moved in the axial direction in accordance with the rotation of the cylinder and thereby carries one of the shift forks with it, so that ultimately a movement of the sliding sleeve concerned and thus the engagement of an associated gear ratio takes place. In accordance with the gear ratio between the control shaft and the intermediate shaft, when the control shaft turns, the intermediate shaft also rotates the sleeve relative thereto, so that in accordance with the shifting sequence of the transmission the shift fingers come into contact with the individual shift forks. Thus, when the electric control element is actuated a sequential upshift or downshift can be carried out.
The previously unpublished DE 10 2009 054 942 by the present applicant proposes an internal shifting device for a geared variable-speed transmission, for engaging one of several shiftable gear ratios of the geared variable-speed transmission, which has a shift sleeve arranged in a rotationally fixed manner but axially movably on a transmission shaft. In this case when the shifting device is actuated, actuating means engage in at least one shift groove provided on a peripheral contour of the shift sleeve, which groove has a curved shape, so that when the transmission shaft is rotated the shift sleeve is moved axially in accordance with the shape of the shift groove. This couples the transmission shaft to a loose wheel positioned near it. Since the shifting device proposed in DE 10 2009 054 942 is explicitly intended for a geared variable-speed transmission for engaging one of several shiftable gear ratios of the transmission and for this purpose a loose wheel is necessarily presupposed, the device is not suitable just as it is for applications outside a geared variable-speed transmission, for example in a one-stage transfer box of a vehicle drive-train.